Currently, to fabricate an optical component, e.g., a photodetector, an optical quality germanium (“Ge”) film is deposited directly on a single crystal silicon (“Si”) substrate or on a silicon on isolator (“SOI”) substrate.
FIG. 1A shows a Ge photodetector film 102 deposited directly on a Si substrate 101 to fabricate a photodetector. Lattice mismatch between germanium and silicon produces defects on an interface 103 between Ge photodetector film 102 and Si substrate 101. As shown in FIG. 1A, Ge photodetector film 102 is adjacent to substrate 101.
FIG. 1B shows a Ge photodetector film 112 grown directly on a silicon substrate 111 through an opening 114 in a silicon dioxide (“SiO2”) insulating layer 113 to fabricate a photodetector. As shown in FIG. 1B, Ge photodetector film 112 over insulating layer 113 is in direct contact with silicon substrate 111 through opening 114 in insulating layer 113.
The optical devices, e.g., photodetectors, formed directly on the semiconductor substrate in a separate process occupy the substrate space that may be needed for other devices. Additionally, forming optical devices, e.g., photodetectors, in close proximity to a substrate introduces substantial optical losses. The optical losses may be in an optical waveguide that carries light to the photodetector, because light may be absorbed in the substrate.
Further, to integrate photodetectors grown in separate processes on the separate substrates, with microprocessor and other circuit chips and devices, flip-chip bonding (to bumps), wire bonding, or other packaging solutions are used. Using the flip-chip bonding, wire bonding, or other packaging solutions introduce parasitics that negatively impact on the performance of the photodetector and other circuit devices.